Application of heart rate variability in evaluation of mental workload / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate if heart rate variability (HRV) can be used to evaluate mental workload.</p><p><b>METHODS</b>Forty-six volunteers were selected to simulate mental work by inputting the random number through keyboards. ECG was recorded by Holter 8800 during the performance and transferred into digital signal. Total power (TP), low frequency (LF), high frequency (HF) were analysed by Holter software.</p><p><b>RESULTS</b>Along with time, the inputting speed increased but accuracy decreased, and was positively correlated with TP, LF (r = 0.851 and 0.827 respectively, P < 0.05), showing a distinct dose-effect relationship. HRV values at rest were higher than during mental work [TP: (2 745.4 +/- 1 301.6) vs (686.2 +/- 420.7) ms(2)/Hz; HF: (670.6 +/- 393.8) vs (202.6 +/- 171.7) ms(2)/Hz; LF: (870.5 +/- 553.7) vs (206.0 +/- 187.9) ms(2)/Hz] indicating that they were decreased remarkably as the mental work started. Then, they were gradually increased with the workload (intensity and time) increased, but still at lower level.</p><p><b>CONCLUSION</b>HRV may be used as a parameter to evaluate mental workload but the change pattern of HRV needs to study further.</p>

Expression of Smads in lung tissue of quartz-induced pulmonary fibrosis in mice / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To observe Smads protein expression in lung tissue of quartz exposed mice and to explore its association with pulmonary fibrosis in silicosis.</p><p><b>METHODS</b>The experimental mice were divided into control and quartz groups. 0.2 g/kg weight of quartz was injected intratracheally in quartz group. Samples were collected at the 1st, 3rd, 5th, 7th, 14th and 28th day after injection. Immunohistochemical methods with quantitative image analysis were used to assay the protein expression of transforming growth factor beta(1) (TGF-beta(1)), Smad 2/3, Smad 4, and Smad 7 protein levels. Protein expression level is presented by positive unit (PU).</p><p><b>RESULTS</b>Smad 2/3 protein expression increased from day 3, reaching its peak level in day 14 [(42.2 +/- 2.4) PU], and decreased gradually. The elevation of Smad 4 protein level began from day 5, and the highest degree came into day 14 [(40.0 +/- 1.8) PU], decreased thereafter. The expression of Smad 7 presented a decreasing tendency at the beginning and reaching the lowest level in day 14 [(33.5 +/- 3.3) PU]. It seemed to elevate in day 28, but was still lower than the controls. There were positive correlation between Smad 2/3, Smad 4 and TGF-beta(1) (r = 0.91, r = 0.71, respectively, P < 0.05) and also between Smad 2/3 and hydroxyproline contents of lung tissue (r = 0.85, P < 0.05) except Smad 7.</p><p><b>CONCLUSION</b>Smad protein may have certain association with pulmonary fibrosis in silicosis.</p>

Analysis of surface electromyography on repetitive lifting task-induced fatigue of back muscles / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>Using surface electromyography (SEMG) technique to evaluate repetitive lifting task-induced fatigue of back muscles.</p><p><b>METHODS</b>Thirteen volunteers lifted and lowered an 8 kg weight from floor to waist level for 100 times. Fatigue in the erector spinae muscles was quantified by comparing the frequency content of the EMG signal during static contractions performed before, and immediately after the 100 lifts.</p><p><b>RESULTS</b>EMG average amplitude rose gradually during 100 lifts, the difference was significant at T10 right (P < 0.05) and L3 left (P < 0.01), the difference was not significant at T10 left and L3 right (P > 0.05). The median frequency intercept at T10 right, T10 left, L3 right, L3 left erector spinae muscles decreased by 2.0% (P > 0.05) 10.9% and 29.9% (P < 0.05), 27.9% (P < 0.01), respectively. The mean power frequency intercept decreased by 9% at L3 left erector spinae muscle (P < 0.05), the decrease was not statistically significant at other sites (P > 0.05).</p><p><b>CONCLUSION</b>Repetitive lifting may induce measurable fatigue in the erector spinae muscles. Erector spinae muscle at L3 is more easily fatigued than at T10. Using the median frequency intercept to assess muscle fatigue is more sensitive than using mean power frequency intercept.</p>

Estimation of intramuscular load of the upper limb in static postures and repetitive work by surface electromyography / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To evaluate the intramuscular loads of the upper limb during static postures and repetitive work by surface electromyography.</p><p><b>METHODS</b>Twenty-six male college student volunteers were recruited for the experiment. The surface electromyography (SEMG) singal were recorded from the brachioradialis, biceps brachii, deltoid and trapezius of right arm during static postures including forward elevating, abducting, extending and a repetitive performance at different height of the bench, and root mean square (RMS) values were educed from the singal.</p><p><b>RESULTS</b>The SEMG amplitudes from forward elevating and abducting were in direct proportion to the angle of the elevating and abducting (r > 0.9, P < 0.01). The maximal voluntary electrical activation (MVE) of the deltoid were 6.4%, 10.1%, 12.6%, 16.2% and 20.8% while the arm elevated forward at an angle of 0 degrees , 45 degrees , 90 degrees , 135 degrees and 180 degrees respectively. The repetitive work showed that the height of the bench and the duration had more effects on deltoid and trapezius than the other muscles. The MVE% of the deltoid were 13.0%, 14.4% and 15.6% while the bench was 74, 79 and 84 cm in height respectively (P < 0.01).</p><p><b>CONCLUSION</b>SEMG which is suitable for determining and reflecting the muscle strain during static postures and repetitive work may be a reasonable indicator for the assessment of manual workload and the ergonomic design.</p>

Immunohistochemical method for the detecting expression of transforming growth factor-beta1 in lung tissues of silica-treated mice / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the protein expression of transforming growth factor-beta(1) (TGF-beta(1)) in lung tissues of silica-treated mice.</p><p><b>METHODS</b>The experimental mice were divided into control and silica groups. 0.2 g/kg body weight of silica was injected intratracheally in mice of silica group. Samples of lung tissue were collected 1, 3, 5, 7, 14 and 28 d after injection. The immunohistochemical method was used to analyze the protein expression of TGF-beta(1).</p><p><b>RESULTS</b>In control mice, the expression of TGF-beta(1) in lung tissue was slightly positive while it was markedly increased in silica-treated mice. The expression was significantly elevated from the 7th day to 14th day. The expression in alveolar macrophages reached the peak on the 5th day [(93.4% +/- 2.8%) vs (42.2% +/- 12.0%), P < 0.01].</p><p><b>CONCLUSION</b>TGF-beta(1) may play an important role in early development of silicosis.</p>

RT-PCR method for detecting the expression of transforming growth factor-beta1 gene in lung tissues of silica-treated mice / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the gene expression of transforming growth factor-beta(1) (TGF-beta(1)) in lung tissues of silica-treated mice.</p><p><b>METHODS</b>The experimental mice were divided into control and silica group. 0.2 g/kg body weight of silica was injected intratracheally in silica group. Samples of lung tissue were collected 1, 3, 5, 7, 14 and 28 d after injection. RT-PCR method was used to analyze the gene expression of TGF-beta(1) in lung tissue of silica-treated mice.</p><p><b>RESULTS</b>The expression of TGF-beta(1) gene in lung tissue elevated from the 3rd day (1.20 +/- 0.15) and the peak value was on the 7th day (1.74 +/- 0.19). Then the expression decreased from the 14th to 28th day. But there was still higher than control until the 28th day.</p><p><b>CONCLUSION</b>TGF-beta(1) may play an important role in silica-induced pulmonary fibrosis.</p>